Publications [#9652] of Eric Sharpe

Abstract:In this article we explain discrete torsion. Put simply,
discrete torsion is the choice of orbifold group action on
the B field. We derive the classification H^2(G, U(1)),
we derive the twisted sector phases appearing in string
loop partition functions, we derive M. Douglas's description
of discrete torsion for D-branes in terms of a projective
representation of the orbifold group, and we outline how
the results of Vafa-Witten fit into this framework. In
addition, we discover some new degrees of freedom that
appear in describing orbifold group actions on B fields, in
addition to those classified by H^2(G, U(1)), and explain
how these new degrees of freedom appear in terms of twisted
sector contributions to partition functions and in terms of
orbifold group actions on D-brane worldvolumes. This paper
represents a technically simplified version of prior papers
by the author on discrete torsion. We repeat here
technically simplified versions of results from those
papers, and have included some new material.